by Carl Zimmer
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The Decode researchers looked for human knockouts in Iceland — and found a lot of them. Nearly 8 percent of Icelanders lack a working version of a gene. All told, the Decode team identified 1,171 genes shut down in Icelandic knockouts.
In a 2012 study, Dr. MacArthur and his colleagues were able to identify just 253 genes knocked out in humans.
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One can find more productive ways to think about genes. As a physician who researches and treats rare genetic disorders, Sharon Moalem, the author of “Inheritance,” sees firsthand how sharply DNA can constrain our lives. Yet “our genes aren’t as fixed and rigid as most of us have been led to believe,” he says, for while genetic defects often create havoc, variable gene expression (our genes’ capacity to respond to the environment with a flexibility only now being fully recognized) can give our bodies and minds surprising resilience. In his new book, Moalem describes riveting dramas emerging from both defective genes and reparative epigenetics.
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Recent rapid growth of human populations predicts that a large number of genetic variants in populations today are very rare, i.e., appear in a small number of individuals. This effect is similar to that of purifying selection, which drives deleterious alleles to become rarer. “}}